Germany is deeply concerned about China’s apparent unwillingness to discuss removing restrictions against the widow of Nobel Peace Prize winner Liu Xiaobo, an embassy source said on Friday, two weeks after the activist died of cancer in custody.

Liu Xia has been under effective house arrest since her husband won his Nobel in 2010. She was allowed to visit him in prison about once a month and remain with him while he was treated for cancer in his final days.

Liu Xiaobo, a veteran of the 1989 Tiananmen Square pro-democracy protests, was sentenced to 11 years in prison in 2009 for “inciting subversion of state power” after he helped write a petition known as “Charter 08” calling for sweeping political reforms.

“The German embassy remains deeply concerned about the apparent unwillingness to discuss lifting restrictions against Mrs Liu Xia, for which the Chinese authorities have been unable to cite any legal foundation,” the source told Reuters.

“A number of ambassadors have repeatedly asked for a meeting with Chinese security organs – so far to no avail,” the source said, adding the embassy had been unable to contact Liu Xia.

Liu Xia’s whereabouts are unknown. Liu Xiaobo’s brother said at a government arranged news conference after his death that Liu Xia was in a poor state of health and not able to appear before the press.

The source said it seemed she was not allowed to speak to anyone by telephone or meet with anyone apart from close family members.

China’s Ministry of Public Security did not immediately respond to a request for comment. It was not possible to contact the Ministry of State Security as it has no website or publicly available telephone number.

“The relevant Chinese government departments will safeguard any of her rights in accordance with the law,” Lu said. “We resolutely oppose any country attempting to use any means to interfere with China’s domestic affairs.”

Diplomatic sources have previously said that, before her husband was sent to hospital, Liu Xia had expressed a wish to go to Germany, in telephone calls with the German embassy.

German Foreign Minister Sigmar Gabriel said earlier this month that China should allow Liu Xia and her brother to leave the country to come to Germany or any other country they wish.